This is Version 1. Contact me if you have suggestions, revisions, etc. to add.
GalCon is a fun tactics game that you can play with people online.
These strategy tips are fairly obvious once you've played the game a bit, I think, but they make the game a lot more fun for newbies. All info is IMO.
I play as 'titus' and 'mimi', and I apparently win ~60-70% of games. If you can get advice from people who win more, or who beat me regularly, take it ;).
The initial moves often determine if you're going to survive more than 30 seconds. There are people who are really good at this, and there are people who seem to suck. I'm not the best, but here's my advice anyway.
Everyone starts with the same home planet production & troop number. So it's easy to determine whether or not you can take out your neighbor: if he's spending a lot of troops taking over planets, you should have a small window of opportunity to nab his home planet.
If you have a superior starting position -- more/better planets -- wait to attack. Build up your strength first. Don't look too strong, though; you may invite attacks from both neighbors.
If you have a weaker starting position, attack immediately and hope you're up against someone who is going to make a mistake. That's the only way you're going to have a chance ;).
You've started out in a gold mine of big fat planets! Hooray, you've got a great chance of winning!
Well, maybe. If you have low-cost big planets available, you're home free: take 'em and start expanding.
If you have high-cost planets nearby -- anything above 10-20 is a high-cost planet in my book -- be careful. One of my favorite things to do is wait for someone to spend 40 or 50 troops on taking a big planet, and then grab it out from under their nose. Then, since I'm often near their home planet, and I know that I now have bigger production than them... yum! Easy meat!
You're basically toast. Your best bet is to hope that no one good starts near you, and/or that your neighbors get distracted by other enemies. If there are some big planets in the middle to take, that's good: but be careful, because your neighbors may take advantage of the transit time to grab your home planet.
Never send 100% of your troops away from your planets unless you're damn sure that your planets are safe.
Transit time has a big effect. (See the starting position advice above, too.) If you send your ships a long way, the enemy has a lot of time to prepare and build up his troops: even if you ship from a planet with even or slightly production, the extra troops produced by the defending planet while your ships are in transit mean that you are more likely to lose the battle than not.
Planets that are close together can support each other much more effectively, because you can shift troops around between them quickly.
If you're up against a much stronger enemy and there's no help in sight, RUN. Concentrate all your troops and roam around the board, grabbing small and/or lightly-defended planets from your enemies. Remember, if they're concentrating on their big enemy across the board, they're leaving their back planets open for the taking. Gauging when and where to strike is an art that I haven't mastered, but I have seen some fantastic comebacks...
(Yes, you can just sit back and die. But that's kind of boring, and you can probably tilt the balance of the game towards or away from people if you attack their back planets cleverly.)
If you have even a marginal superiority, set your phasers on 30% and go after every planet the enemy has. Unless they're very good, they will get flustered and try to protect their big planets; or they may try to attack your big planets. Meanwhile you'll take all the rest of their planets, at which point you can crush them at will.
If you're down to a Galcon Standoff -- everyone has expanded to UN-sanctioned borders and is sitting there starting at each other -- you have a few options. If you've clearly got more planets than the other people, waiting is your best option. You'll grow incrementally more stronger than them. If they team up, try to take one of them out as quickly as possible. Usually you can get one of them to backstab each other.
If you're weaker, try to ask the other weak player for a truce while you take out the bigger player. This will often invite an immediate attack from the biggest player, but that's ok: if the other weak player is even remotely sane, they'll attack the bigger player while he's busy with you.
If you all look roughly the same strength, try to invite an attack by sending a few hundred troops at some minor planet that you have a chance of taking. Then sit back, defend, and wait for an opening.
In team play, you're part of a team of people that can share troops. You can see (but not direct) the troops on the planets owned by your teammates. The only way you can share troops is by "attacking" their planets with yours; you can't take or direct other people's troops.
Team games are very different, and if you don't hold up your end of things your teammates will quickly get frustrated with you. If you don't feel up to cooperating with other people, don't play in a team game!
One of the first team moves you make should be to take out any neighboring enemies as quickly as possible. If you're not next to an enemy, ship a bunch of troops to any neighbor that is next to an enemy. You'll be able to take that enemy out virtually instantly.
Don't focus just on your own battle. (I know, easier said than done...) If you focus too much on taking down an enemy, their own teammates may be attacking your back planets.
My favorite role in team play is to build up a big reservoir of planets, then support my teammates on either side. You get credit for wins either way, and if you have a good starting position you can do very well by playing this way. Plus, your teammates will be very happy with you.
Unbalanced team numbers are inherently unfair, e.g. 4 on 3. I very rarely see the team with fewer players win. Why this is should be obvious: the team with one or more additional players can immediately gang up on at least one member of the other team.
There is no way to divide 3, 5, 7, 9, or 11 people into two teams.
There is no way to divide 3, 5, 7, or 11 people into fair teams. (They're prime numbers.)
Finding your home planet when the game starts can be tricky, especially if you're not a primary color. I start every game by immediately selecting everything on the screen; that highlights my home planet.
Run. Run. Run. If you're about to die, leave your planets and ask one of your teammates to find a home for you. Keep in mind they may be busy at the moment ;). It's in everyone's interest to keep team member's alive, though: the more different people attacking the enemy team, the more likely it is that you'll win.
You get credit for the team win even if you die before your team wins, as far as I can tell.
Keeping many troops on a planet doesn't increase its production.
Leaving before you lose still counts as a loss on your stats, if you care about that sort of thing.
There is no second place. Don't play for it.